Thiazole and thiophene derivatives have been used as therapeutic agents for such things as to treat neurological disorders, migraine, pain, cancer, inflammation, and autoimmune disease. Aminothiazole compounds substituted at 5th position with substituents such as acyl, aroyl, nitro etc. have also been used for these purposes.
There is abundant evidence that T-lymphocytes orchestrate both the initiation and the propagation of the immune response through the secretion of protein mediators known as cytokines and chemokines. Cytokines and chemokines have been implicated in a number of inflammatory diseases. Inappropriate responses of T-lymphocytes have been associated with a range of immune-related diseases, including allergies, autoimmune diseases, asthma, psoriasis, rheumatoid arthritis, and transplant rejections.
Major functions of T lymphocytes include assisting B cells in the production of antibodies, cooperating with macrophages and related cell types to enhance their capacity to destroy microorganisms, acting as antigen-specific cytotoxic cells, and producing a family of cytokines and chemokines that have profound effects on the function of other cell types. The T cell has a highly-evolved specific antigen recognition system. T cells are activated following engagement of the T cell receptor (TCR), and the receipt of additional co-stimulatory signals. There are specific cytokines and growth factors that stimulate T cells to proliferate and differentiate.
Transcription factors regulate inducible gene expression. In activated T cells, transcription factors such as activator protein-1 (AP-1) regulate interleukin-2 (IL-2), IL-3, GM-CSF, and matrix metalloproteinases, while nuclear factor-κB (NF-κB) regulates transcription of the proinflammatory cytokines IL-1, IL-6, IL-8 and tumor necrosis factor α (TNFα). The ability of transcription factors to bind DNA and modulate gene transcription is tightly regulated in normal cells. Signal transduction pathways regulate cellular responses to stress and play a critical role in inflammation.
The AP-1 transcription factor comprises homo- or heterodimer proteins of the leucine zipper family. The leucine zipper family includes Fos (Fra-1, Fra-2, Fos-B, Fos-B2 and c-Fos), and Jun (c-Jun, JunB and JunD). The Jun family of proteins is widely known, and forms both homo- (Jun-Jun) and hetero- (Jun-Fos) dimers. Three mitogen activated kinase pathways (MAP) (ERKs, JNKs and p38) directly up regulate Fos family genes by phosphorylation. It appears that JNK pathways indirectly up regulate c-Jun expression.
The activated AP-1 complex translocates into the nucleus, where it initiates cytokine production. A variety of extracellular signals stimulate AP-1 activity, including tumor promoters, UV irradiation, growth factors, cytokines, neurotransmitters, and Ras oncoprotein.
The NF-κB transcription factor belongs to Rcl family of proteins, which primarily comprises homo- and heterodimeric proteins. The most commonly found combinations are p50/p65 heterodimers and p50/p50 homodimers. NF-κB is normally present in the cytoplasm in an inactive form, bound to inhibitory kappa B (IκB) protein. Several extracellular stimuli such as TNFα, IL-1, certain mitogens and stress factors activate the signaling pathway leading to IκB kinase (IKK), which phosphorylates IκB. Phosphorylated IκB undergoes degradation by 26S proteosome, releasing NF-κB, which translocates to the nucleus and initiates transcription.
Nuclear factor of activated T cells (NFAT) transcription factors play a critical role in transcriptional regulation of IL-2, IL-3, IL-4, IL-5, IL-8, IL-13, TNFα, and GM-CSF. NFAT proteins are expressed in T cells, B cells, NK cells, mast cells, macrophages, and endothelial cells. NFAT's nuclear functions are regulated by cooperative interactions with AP-1. When certain ligands bind to receptors such as Fcg receptors on macrophages and NK cells, the histamine and thrombin G protein coupled receptors on endothelial cells, and Fce receptors on mast cells and basophils, phospholipase C is activated and inositol triphosphate (IP3) is generated. Calcium is then mobilized, and calcium- and calmodulin-dependent phosphatase calcineurin are activated. Calcineurin regulates the localization and transcriptional function of NFAT via dephosphorylation. Several kinases, including JNK, ERK, and p38, inhibit NFAT activation via phosphorylation at the NFAT regulatory domain where calcineurin binds.
Since many diseases are caused by the inappropriate production of proteins, many prior therapies have focused on inhibiting the function or activity of individual effector proteins. These treatments have not always proved effective, and have sometimes been associated with undesirable side effects.
There is an unfilled need for new compounds to treat inflammation, autoimmune diseases, and cancers. There is an unfilled need for compounds that will inhibit the transcription of one or more of AP-1, NF-κB, and NFAT transcriptional activation in T cells. Each of these transcription factors is regulated by a distinct signaling pathway involving several proteins including different kinases. There is an unfilled need for compounds that also inhibit the kinase(S) that regulates the activation of the transcription factors AP-1, NF-κB, and NFAT.
Transcriptional Inhibitors, Post-Transcriptional Inhibitors, and Multi-Pathway Inhibitors for Cancer Treatment
Most current anticancer treatments and drug discovery programs focus on targeting a single gene (for example, her2/neu or VEGF) or a single pathway (for example, kinase activation). However, cancer is a multifactor process involving the expression of many different proteins. This is reflected in the observation that many current clinical trials involve combinations of different drugs. A significant drawback to combined therapies is that each drug typically has its own associated side effects, and the combination of multiple drugs can lead to an increase in the number or intensity of side effects. There is an unfilled need for single compounds that can act upon multiple pathways and targets involved in cancers, for example, single compounds that can act against angiogenesis, growth, and metastasis, processes which involve diverse proteins (for example, VEGF, her2/neu receptor, and matrix metalloproteases, respectively). Classical drug discovery approaches, targeting each protein separately, are unlikely to find single compounds that serendipitously act upon other targets and pathways. There is an unfilled need for single compounds to inhibit the production of different proteins involved in different pathways.
U.S. Pat. No. 6,630,589 discloses screens for identifying small molecules capable of preventing the production of proteins at the post-transcriptional level, and discloses a small molecule that blocked her2/neu protein synthesis. Although the precise mechanism of action of this molecule was not elucidated, it may involve translational regulation. The regulation of other poorly translated proteins in cancer may be due to increased levels of the cap binding protein, eIF4E, which is often found in cancer cells, and the levels of which have been correlated with clinical recurrence. There is an unfilled need for compounds to target highly cap-dependent translation pathways, as such compounds could affect many genes involved in cancer growth and progression with reduced effects on normal cells.
Transcriptional regulation also plays an important role in the production of proteins involved in cancers; for example, NF-κB- and AP-1-inducible genes are targets for the development of anticancer agents. There is an unfilled need for single compounds that selectively inhibit the expression of multiple genes involved in cancers. There is an unfilled need for small molecules for treating cancers. Many current clinical trials involve relatively large molecules, such as monoclonal antibodies, recombinant proteins, peptide vaccines, siRNAs, and antisense RNA. While many of these approaches have shown promise, particularly monoclonal antibodies and recombinant proteins, they typically require injection and are usually expensive. Peptide vaccines and siRNAs are still in early stages of development, but would presumably also require injections and be expensive. Gene therapy and antisense strategies have had more failures than successes.
The usual approach in mechanism-based drug discovery is first, to optimize molecular properties against a single target, and then, to modify the molecule to have better “drug-like” properties. However, cancer is a complex disease that results from perturbations in as many as six different intracellular regulatory systems. A drug that affects a single target or pathway may therefore not be very effective against the heterogeneous distribution of cellular phenotypes that is typical of most cancers. The individual compounds of this invention affect multiple targets and pathways. Given the diversity of the proteins involved in different pathways, the conventional drug discovery approach, targeting a particular protein, is unlikely to develop single compounds to affect multiple pathways. The novel compounds instead prevent the production of critical proteins in multiple pathways by targeting transcriptional or post-transcriptional regulatory processes.
General transcriptional inhibitors, those affecting transcription of all mRNA, would be too toxic. Inhibition of specific transcriptional factors is desirable. NF-κB and AP-1 are the targets for the novel anti-cancer therapeutics. NF-κB and AP-1 pathways play an important role in promoting metastases, tumor progression, angiogenesis, and chemoresistance. Many genes involved in cancer (e.g., IL-6, IL-8, MMP-9, COX-2, and MCP-1) are regulated by the combined action of NF-κB and AP-1. Activated AP-1 and NF-κB are found in transformed keratinocytes, pancreatic cancers, and head and neck squamous cell carcinoma cell lines.
Inhibition of NF-κB and AP-1 by various natural products, including macrolides, endovanilloids, and EGCG has been demonstrated to have anti-inflammatory effects. EGCG has been studied for anticancer activities. Curcumin, derived from the plant Curcuma longa, has been demonstrated to down-regulate NF-κB and AP-1, and is also being studied as an anticancer agent. While existing work with these compounds demonstrates that inhibitors of NF-κB and AP-1 can be useful as anti-cancer agents, natural products can be costly to purify and usually are not very potent, requiring high dosages to elicit substantial anti-cancer activity. Structural modification and formulation of these natural products is a possibility in principle, but has proven to be challenging in practice. Other genes that are involved in angiogenesis and tumor growth are constitutively transcribed and regulated at the translational level in cancer cells. Thus targeting NF-κB and AP-1 alone may not inhibit many of the critical targets in cancer growth and metastasis.
The translation initiation factors eIF4E, eIF4F, and eIF4G, and mTOR have been shown to play a significant role in tumor progression. The factor eIF4E is elevated in most human breast and head and neck cancers, and its overexpression has been correlated with elevated angiogenic growth factors and by hypoxia. In head and neck tumors, elevated eIF4E levels have been associated with increased levels of VEGF, FGF-2, microvessel density, and poor outcome. In breast cancer, high eIF4E levels have also been associated with poor clinical outcome.